1. Field of the Invention
The present invention relates to image capturing apparatuses and control methods thereof, and particularly relates to image capturing apparatuses capable of reading out a pair of signals based on light beams from pixels that have passed through different pupil areas of an optical system, and to control methods thereof.
2. Description of the Related Art
Techniques for implementing both a focus detection function and image signal acquisition using a single image sensor have been known for some time, and a technique in which information acquisition pixels for focus detection can also be used as image acquisition pixels for acquiring an image signal has been proposed as an example of such (for example, see Japanese Patent Laid-Open No. 2007-325139). According to this technique, the information acquisition pixels are divided into four regions in the horizontal and vertical directions, and when an image is to be acquired, an image signal is obtained by adding together signals from the four regions obtained through this division. Meanwhile, when controlling the focus, the signals of two of the four regions obtained through the division in either the horizontal or vertical direction are added together; pupil division is carried out in the pixels as a result, and the signals are used as focus control signals according to a phase difference detection method.
However, with an increase in the number of pixels in image sensors, it is necessary to read out a great number of pixel signals within a predetermined amount of time; on the other hand, systems are experiencing increasing burdens due to increases in the output rates of image sensors, increases in the number of output channels, and so on. For example, there is a problem in that the complexity of signal delay amount adjustment between channels increases due to an increase in the number of output channels or an increase in the signal output rate. Because such a configuration increases the number of signal readouts, the system will experience an increased burden particularly in the case of an image sensor in which single pixels are configured of multiple photoelectric converters and a pupil division readout function is provided.